The present invention relates to methods and apparatus for compression, transfer through a limited bandwidth medium, and expansion of digitalized television picture signals at real time rates up to standard broadcast frame rates. More particularly, the present invention relates to methods and apparatus for television picture single pass scene adaptive compression, transfer and expansion with two dimensional transformation in conjunction with compression coding schemes wherein rate buffer feedback is effectively utilized to provide optimalized compression normalization factoring in real time without undue degradation of restored picture imagery and with minimized hardware implementation requirements.
Digital coding techniques are increasingly employed in processing television signals for transfer over noisy transmission channels. Digital data streams may be made essentially free of noise degradation, and this advantage in the transmission of digitized information has been advantageously utilized over long, noisy transmission paths. Thus, it is an increasingly common practice today to digitalize broadcast television signals for transmission and relay through otherwise noisy long distance paths, such as stationary earth satellites many thousands of miles away from the earth.
To digitize a television signal, a significant number of bits, 4, 5, 6 or even more, may be required to provide for the proper range of gray scale of each of the hundreds of thousands of separate picture elements (pixels). Consequently, data rates for digitalized television signals are far in excess of the highest frequency components of analog television signals. It is not unusual to find in a digitalized televsion communications link, a required video bandwidth of 40 megabits per second. While digitalized television transmission formats advantageously overcome the signal to noise problem inherent in analog transmission over similar path lengths, the substantial bandwidths for such digitalized signals often occupy the entire bandwidth capability of the communications link. If the communications link is an earth satellite in stationary orbit above the earth, the video signal typically occupies the entire transponder bandwidth of the satellite, with very few channels, if any, left over for other uses. Thus, need has arisen for a practical yet effective way to reduce the bandwidth of digitalized television signals to provide for more channels within a communications path such as an earth satellite.